Abstract:
GNRH significantly inhibits proliferation of a proportion of cancer cell lines by activating
GNRH receptor (GNRHR)-G protein signaling. Therefore, manipulation of GNRHR signaling
may have an under-utilized role in treating certain breast and ovarian cancers. However, the
precise signaling pathways necessary for the effect and the features of cellular responses
remain poorly defined. We used transcriptomic and proteomic profiling approaches to
characterize the effects of GNRHR activation in sensitive cells (HEK293-GNRHR, SCL60)
in vitro and in vivo, compared to unresponsive HEK293. Analyses of gene expression
demonstrated a dynamic response to the GNRH superagonist Triptorelin. Early and midphase
changes (0.5–1.0 h) comprised mainly transcription factors. Later changes (8–24 h)
included a GNRH target gene, CGA, and up- or downregulation of transcripts encoding
signaling and cell division machinery. Pathway analysis identified altered MAPK and cell
cycle pathways, consistent with occurrence of G2/M arrest and apoptosis. Nuclear factor
kappa B (NF-kB) pathway gene transcripts were differentially expressed between control and
Triptorelin-treated SCL60 cultures. Reverse-phase protein and phospho-proteomic array
analyses profiled responses in cultured cells and SCL60 xenografts in vivo during Triptorelin
anti-proliferation. Increased phosphorylated NF-kB (p65) occurred in SCL60 in vitro, and
p-NF-kB and IkB3 were higher in treated xenografts than controls after 4 days Triptorelin.
NF-kB inhibition enhanced the anti-proliferative effect of Triptorelin in SCL60 cultures.
This study reveals details of pathways interacting with intense GNRHR signaling, identifies
potential anti-proliferative target genes, and implicates the NF-kB survival pathway as a
node for enhancing GNRH agonist-induced anti-proliferation.
